Guide vanes from stators of gas turbines consist of high-alloy metal and are often manufactured, as described, for example, in U.S. Pat. No. 4,015,910, as individual guide vane elements which are then connected with each other to form a guide vane ring. In most cases, such an individual element comprises at least one vane blade, as well as an outer and an inner platform attached to the vane blade. If such elements are connected with each other to form an entire guide vane unit, the respective outer and inner platforms form the cover bands that extend cylindrically and delimit the area through which the operating gases flow. The manufacture by elements facilitates and simplifies the production process. In particular, number, size, and complexity of the casting molds are reduced.
As described, for example, in EP 0 949 404 A1, the elements can be less susceptible to breaks caused by thermal and mechanical loads during operation in their combined form, and also can be easily replaced. The individual elements are also much easier to finish, which is particularly advantageous for the drilling of cooling channels, as they are required for film cooling.
The problems with such guide vane elements usually occur in the connection zones between the platforms. The elements or their platforms should be joined tightly and fixed to each other so that a tight unit of guide vanes is created and a cover band is formed that prevents the uncontrolled exchange of the operating gases and cooling gases separated from the cover band. However, the connection and its geometry must not be so rigid and limiting that the mechanical and thermal loads occurring as a result of the temperature differences between the hot operating gases and cold cooling gases during operation result in material fatigue or even breaking of the elements.
EP 0 903 467 A2 describes, for example, pairs of guide vane blades that can be interconnected with flanges, in which the connection is designed so that the meshing prevents a thermal load and the associated breaks of the elements during operation while simultaneously preserving the tightness of the cover bands.